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Chemistry Test 255
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Chemistry Test 255
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  • Question 1/10
    4 / -1

    Identify the pair of elements with the highest and lowest electronegativity respectively

    Solutions

    Fluorine (F) is the element with highest electronegativity, lying at the extreme right in the second period.

    Francium (Fr) is the most electropositive or least electronegative element, lying at the bottom left of the periodic table.

     

  • Question 2/10
    4 / -1

    Which of the following facts regarding boron and silicon is not true?

    Solutions

    The halides of B and Al are hydrolysed.

     

  • Question 3/10
    4 / -1

    Electrolysis of dilute aqueous NaCl solution was carried out by passing 10 mA current. The time required to liberate 0.01 mol of H2 gas at the cathode is (1 F = 96500C mol−1)

    Solutions

    2H2O + 2e− → H2 + 2OH−

    For 0.01 mole H2 0.02 mole of electrons are consumed

    charge required = 0.02 × 96500 C = i × t

     

  • Question 4/10
    4 / -1

    The rate of reaction becomes double when its temperature is raised from 300 K to 330 K. The activation energy of the reaction is (Given: log 2 = 0.30)

    Solutions

     

  • Question 5/10
    4 / -1

    An oxide of nitrogen is reddish brown and paramagnetic at room temperature but it decolourises and also loses its paramagnetism on freezing it. The oxide at room temperature is

    Solutions

    2Pb(NO3)2 → 2PbO + 4NO2 + O2

    i.e. can be prepared by heating heavy metal nitrate of Pb(NO3)2. It is a red brown gas but on cooling below 273 K converts to colourless liquid and retains as dimer. In NO2 molecules 17 valence e−are there (12 that of O & 5 that of N) i.e. one e−unpaired results to paramagnetic nature. So this is an odd e−molecule on being dimer with even e−becomes stable & loses paramagnetic characteristics.

     

  • Question 6/10
    4 / -1

    Ethanal reacts with HCN and the addition product so obtained is hydrolyzed to form a new compound. This compound shows

    Solutions

    The asterisked carbon is 'chiral'.

     

  • Question 7/10
    4 / -1

    The correct combination is:

    Solutions

     

  • Question 8/10
    4 / -1

    On treatment of the following compound with a strong acid, the most susceptible site for bond cleavage is

    Solutions

    The most susceptible site for bond cleavage is O2 - C3 as this cleavage would result in a 2o carbocation which is more stable.

     

  • Question 9/10
    4 / -1

    Haemoglobin and gold sol are examples of:

    Solutions

    Haemoglobin and gold sol both are colloids and always carry an electric charge. Haemoglobin is a positively charged sol, because in hemoglobin, Fe2+ ion is the central metal ion of the octahedral complex. All metal sols like Au-sol etc. are negatively charged sols.

     

  • Question 10/10
    4 / -1

    The major product of the following reaction is

    Solutions

    This is an example of E2 elimination.

    Conjugated diene is formed with phenyl ring in conjugation which makes it very stable.

     

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